Weld joint backing and method of welding with same



p l 1965 J. N. CORDEA ETAL 3,180,021

WELD JOINT BACKING AND METHOD OF WELDING WITH SAME Filed Nov. 21, 1962 My. BY d.

M 6. ewM

ATTORNEYS VENTORJ' United States Patent 3,180,021 WELD JGENT BACKHJG AND METHQD 0F WELDING WITH SAME James N. Cordea and Robert M. Evans, Columbus, and Perry .ll. Rieppel, Worthington, Qhio, assignors, by

side weld face.

covered upon subsequent weld passes.

It is a further object of the present invention to provide a backing material which results in weld having a flat to concave underside which does not entrap slag.

Another object of the present invention is to provide proper-ties of the weldment.

from the shot.

5 a backing material which improves the quality of la weld, meme assignments, flit? United glflieg Of America as and which prevents the penetration of the welding matelepregeflied by the 'y the y rial into the backing material.

Filed 1962, lilo-339,386 In the drawing referred to below, we have shown a 4 Ciaims- (CL preferred embodiment of our invention, which is given The present invention relates generally to improveby way f am ne and notiby limitation, ments in the art of welding and particularly relates to I th drawing; loose particle backing materials used to support molten FIG, 1 i a cross sectional view of two member to weld metal in the joints of material being welded. be welded together with loose backing particles of the It has heretofore been common practice in the welding present invention held in the joint gap of the two memarts to apply a back-up material to the under surface bers, of members or parts to be welded. This material is se- :FIG. 2 is a cross sectional view of one of the sphericured in a suitable manner along the joint gap formed cal, specially coated, metallic particles used in the joint by the members to be welded to prevent molten weld gap of FIG. 1 as a backing material. metal from passing through the joint gap. However, FIG. 3 is :a cross sectional view of the two members serious handicaps and disadvantages have been encounof FIG. 1 and the root weld pass with the backing retered in the use of prior art backing material. moved.

Thus, for example, a solid copper strip or bar may FIG. 4 is a cross sectional view of two members welded be used for a backing. However, the joint tit-up of together with the root weld utilizing a prior art solid the elements to be welded must be aligned or positioned backing bar. within close tolerances if the underside of the root weld Referring now more particularly to the drawings in pass is to be uni-form. -T his is a costly and time-conwhich like reference characters refer to like parts, FIG. suming operation since in many instances complicated I discloses two elongated metallic members 1 and 3 structures require extensive machining of both the backsuch as manganese-molybdenum armor plate to be welded up and the elements to be welded for proper tit-up. Also, together. These members have been positioned side by copper pickup into the weld is often encountered, which 39 side and have opposed beveled edges which form theremust be removed by the extensive grinding of the underbetween what is known in the art as a double-V groove.

Obviously, the edges could be prepared to form a dou- Solid steel material is also used as a backing material. hie-U or other well known type groove. In order to This material becomes an integral part of the weld joint accomplish the objects of the present invention, an elonafiter welding. The use of such backing material also gated holding strip 5, which may be self-adhesive, is requires close :fit-up in order to eliminate bad notches secured to the underside of elongated members 1 and and defects which can result in weld cracks. 3. This strip is flexible and can be used on members Backup materials of prior art loose particles such as having curved surfaces without any special preparations, flake iron powder and granular iron powder have hereto such as machining. As shown, the strip 5 is wide enough fore produced undesirable root welds because the weld to extend from one member to the other to form 'a supmetal penetrated into this backing and resulted in welds port .for the specially prepared loose particle backing having a rough and convex underside. This convex material 7, described below, which is placed in the groove underside forms a bead which entraps slag which must formed between elements 1 and 3. FIG. 2 shows a be removed by laborious and costly methods or else cross sectional view of a single particle :of the backing Slag remaining as material '7. This material is formed from small spheriin the weld joint causes joint weaknesses and possible cal steel shot 9 which is covered with a coating '11 havtailure. Pure silica sand, another loose particle mateing a melting point substantially higher than that of the rial, produces a thick slag layer between the backup and shot for .a purpose described below. weld which is very difiicult to remove. Silica inclusions The following are typical compositions of some of these are picked up by the weld metal and lower the impact shot 9:

Chemical Composition of Shot (Percent) Type of Steel Shot 0 Mn Si Ni Mo Vi'slP Cr Fe Managnese-molybdenum Armor Shot-30 +40 Inesh .27 1.80 .70 .54 .53 .022 .007 Remainder. Electrode Shot Spec. MIL 230-10-30 +40 mesh .08 1.00 .32 .75 .30 .10 .022 .003 Do. A-632 Steel Shot -40 +50 mesh .08 1.33 .50 1. 32 .42 .010 .010 .12 Do. A-675 Steel Shot s0 +40 mesh .10 .95 .45 .025 .025 Do.

Backing particles formed To produce a coating on these shot which melts at a by commercial steel shot result in welds which hot crack higher temperature than the shot itself, a high temperathrough the center area. This cracking probably is caused ture aluminum paint can be utilized. This paint can by the weld pickup of carbon, phosphorus and sulfur have the following composition:

Percent It is therefore an object of the present invention to Aluminum paste 22.5 provide a loose particle backing material which will com- Petroleum resin 19.3 pensate for poor -fit up and misalignment of material to Coal tar solvent 8.6

be welded.

Petroleum spirits 49.6

Before applying the coating, the shot, which are substantially spherical and equal in size, have their surfaces acid-cleaned. The shot are placed in a suit-able container after which an appropriate amount of the paint is added. The container is closed and agitated until all of the shot particles are completely covered with a thin layer of the paint. The amount of aluminum paint required to coat the shot is approximately 4 lbs. per ton of shot and is less than 0.2 percent of the shot in weight. After the coating, the shot is baked at 325 F. for one hour. Mos-t of the resin, solvent, and petroleum spirits are driven from the aluminum paint during this baking period, leaving essentially a thin layer of aluminum which will oxidize readily.

A typical shot particle is shown in cross section in FIG. 2 wherein the spherical steel shot is shown with the aluminum oxide coating 11 adhering to the outer surface of the shot 9. This coating melts at a temperature of 2015 C., substantially higher than the melting temperature of the steel shot listed in the schedule above.

Before the Welding is begun, the holding strip 5 is applied to the underside of members 1 and 3. An appropriate amount of the shot is placed in the groove formed by the edges of the plate members on the holding strip. As shown in FIG. 1, the shot particles are poured to fill the lower V of the double-V groove and so that the top layer of particles is level with the root of the groove.

With the backing thus in place the root weld is placed in the groove on the backing. The intense heat utilized in depositing the welding metal in the groove will melt at least the uppermost layer of the backing particles. The oxidized aluminum coating on the shot will substantially increase the surface tension of the uppermost initial thin layer of molten shot that will give necessary support to the slag layer which will be formed between the weld metal and the backing material. This slag comes in part from the electrode during welding and backing material. The viscosity of this slag layer is substantially increased by the shot coating and the slag layer holds up the weld metal in the center of the root gap long enough to Wet the sides of the base metal. The cohesive forces between the supporting molten backup material is greater than the adhesive forces between the backup material and the base metal, and thus, a convex meniscus is formed by the molten backup material. This convex meniscus favors the wetting of the sides of the base metal by the weld metal to create a weld with a concave underside. Thus, the surface of the molten backing material and the slag layer of increased viscosity play important roles in obtaining a weld contour which will be flat to convex and will not form a bead to entrap slag.

The shape of the backing particles also plays an important role in forming welds having concave underside. The spherical particles 12 when placed in the groove provide many heat insulating air pockets. Thus, the loose particle backing material 7 will not conduct heat as efliciently and quickly as the base metal. When the molten weld is placed in the groove, it readily flows along and wets the heat conductive faces of the base metal while the less conductive backing tends to resist weld penetration.

The backing particles 12 should also be similar in size to produce a fairly smooth concave underside. This is because weld metal penetration, if any, in the backing becomes more uniform as size distribution of the backup particles is reduced. Thus, when particles 12 are all substantially equal in size, the under contour of weld 13 is relatively smooth when compared to a weld made using different sized backing particles.

When the weld material which has been placed in the groove of FIG. 1 hardens, the base metals 1 and 3 are joined. As shown in FIG. 3, portion 13 of FIG. 3 is the fused Weld metal, while sections 14 on either side of the fused weld represent zones which have been affected by the heat used in applying the weld metal in the groove. As shown in FIG. 3, the weld base the desired concave underside 15 with no slag entrapment. The slag layer (not shown) produced during the welding is fairly uniform in thickness and can be easily removed by scrubbing with a wire brush or by any well known method desired.

FIG. 4 shows a typical prior art weld 19 made using a metallic backing bar 17 which had to have machined faces 22 for close fit. The heat affected zones of members 25 and 26 are represented at 20. The weld 19 has a convex underface 23 which provides grooves that entraps thick slag layers 21. This thick slag is difficult to remove requiring a laborious and time-consuming filing process. Often slag particles which remain in the grooves are covered upon subsequent passes and result in a weakened Weld. Furthermore, the metallic backing bar 17 itself may become fused with the weld metal and, if undesirable, will have to be removed by chipping and grinding.

Summary It is believed that the most important aspect of the present invention is the coating of the shot surface with a material which will offer the optimum backing properties. The coating on the shot surface is responsible for the quality of the weld produced. Several possible effects of the shot coating are as follows:

(1) The viscosity of the slag layer between the backup and weld metal is increased by the shot coating so that the weld metal is held up in the weld junction long enough to wet the sides of base material.

(2) The surface tension or the thin molten layer of shot under the weld metal is increased and thus favors the wetting of the bevel faces by the molten weld metal because of the condition of lower surface tension existing in that area.

(3) The coating on the shot acts as an insulator, keeping heat in the weld junction longer than usual, thus favoring more wetting of the base metal bevel faces by the weld metal.

The total effect is believed to be a combination of the three effects listed above in addition to the particle shape and particle size homogeneity. Any coating which offers these properties will work satisfactorily. It is, of course, apparent that coatings other than aluminum oxide which exhibit the properties 1-3 above may be used to coat the spherical particles. One such coating is sodium silicate (water glass) which produces a concave undersurface but a thicker slag layer.

Having described our invention we claim:

1. In the construction of a joint wherein two ferrous members having a gap therebetween are to be welded together the combination comprising:

a removable substantially planar adhesive strip which is secured directly to each of said members, whereby said adhesive strip acts as a bridge and support member across said gap until the weld solidifies wherein it is thereafter removed;

a plurality of particles in intimate contact with said adhesive strip wherein said particles partially fill the gap space, and thereby provide a backing means for the weld;

said particles being formed of an inner portion of steel shot and an outer portion of oxidized aluminum, with said inner portion being in the range of 20 to mesh;

said outer portion of said particles having a melting point higher than the inner portion, with the approximate melting point being at 2015 C. whereby upon the weld in said gap reaching the melting point of said outer portion, said outermost layer of particles will melt and increase the surface tension of the adjacent layer of particles thereby providing a molten smooth support surface for the weld material until the weld solidifies after which said backing and particles are removed.

2. The combination as set forth in claim 1 wherein said members to be welded have opposed vertical planar faces having a beveled portion adjacent said directly attached adhesive strip, thereby forming a trapezoid-shaped receptacle for said particles.

3. The combination as set forth in claim 2 wherein the weld is formed across said vertical planar faces, is concave in cross section, and blends into said beveled portions.

4. In a method of welding two abutting ferrous members the steps comprising:

selecting two members having substantially vertical planar ends;

beveling one edge of each of said members thereby forming a substantial relief from said vertical planar ends; applying an adhesive member, directly to each of said members whereby the gap therebetween is bridged and a trapezoid-shaped receptacle is formed;

selecting steel shot in the range of -20 to +50 mesh,

with said shot being previously coated with an oxidized aluminum coating;

filling the formed receptacle with said coated steel shot to the point where said beveled portion begins, thereby forming a smooth support surface for the weld at the junction of the vertical planar surfaces and the beveled edges;

fusion-depositing weld metal in and along said gap on the top layer of said shot; and

removing said adhesive and shot upon weld solidification whereby a smooth concave weld surface is formed.

References Cited by the Examiner UNITED STATES PATENTS 2,033,240 3/36 Hardy.

2,068,658 1/37 Cox.

2,230,369 2/41 Wise 113111 2,323,160 6/43 Stecker et al 29--490 X 2,331,689 10/43 Hodge.

2,362,505 11/44 Smith.

2,691,952 10/54 Wilson et a1.

2,916,001 12/59 Chyle et a1.

2,979,808 4/61 Booth 113-99 X 2,985,411 5/61 Madden.

JOHN F. CAMPBELL, Primary Examiner. 

1. IN THE CONSTRUCTION OF A JOINT WHEREIN TWO FERROUS MEMBERS HAVING A GAP THEREBETWEEN ARE TO BE WELDED TOGETHER THE COMBINATION COMPRISING: A REMOVABLE SUBSTANTIALLY PLANAR ADHESIVE STRIP WHICH IS SECURED DIRECTLY TO EACH TO SAID MEMBERS, WHEREBY SAID ADHESIVE STRIP ACTS AS A BRIDGE AND SUPPORT MEMBER ACROSS SAID GAP UNTIL THE WELD SOLIDIFIES WHEREIN IT IS THEREAFTER REMOVED; A PLURALITY OF PARTICLES IN INTIMATE CONTACT WITH SAID ADHEXIVE STRIP WHEREIN SAID PARTICLES PARTIALLY FILL THE GAP SPACE, AND THEREBY PROVIDE A BACKING MEANS FOR THE WELD; SAID PARTICLES BEING FORMED OF AN INNER PORTION OF STEEL SHOT AND AN OUTER PORTION OF OXIDIZED ALUMINUM, WITH SAID INNER PORTION BEING IN THE RANGE OF -20 TO +50 MESH; SAID OUTER PORTION OF SAID PARTICLES HAVING A MELTING POINT HIGHER THAN THE INNER PORTIONS, WITH THE APPROXIMATE MELTING POINT BEING AT 2015*C. WHEREBY UPON THE WLD IN SAID GAP REACHING THE POINT OF SAID OUTER PORTIONS, SAID OUTERMOST LAYER OF PARTICLES WILL MELT AND INCREASE THE SURFACE TENSION OF THE ADJACENT LAYER OF PARTICLES THEREBY PROVIDING A MOLTEN SMOOTH SUPPORT SURFACE FOR THE WELD MATERIAL UNTIL THE WELD SOLIDIFIIES AFTER WHICH SAID BACKING AND PARTICLES ARE REMOVED.
 4. IN A METHOD OF WELDING TWO ABUTTING FERROUS MEMBERS THE STEPS COMPRISING: SELECTING THE TWO MEMBERS HAVING SUBSTANTIALLY VERTICAL PLANAR ENDS; BEVELING ONE EDGE OF EACH OF SAID MEMBERS THEREBY FORMING A SUBSTANTIALY RELIEF FROM VERTICAL PLANAR ENDS; APPLYING AN ADHESIVE MEMBER, DIRECTLY TO EACH OF SAID MEMBERS WHEREBY THE GAP THEREBETWEEN IS BRIDGED AND A TRAPEZOID-SHAPED RECEPTIABLE IS FORMED; SELECTING STEEL SHOT IN THE RANGE OF -20 TO +50 MESH, WITH SAID SHOT BEING PREVIOUSLY COATED WITH AN OXIDIZED ALUMINUM COATING; FILLING THE FORMED RECEPTABLE WITH SAID COATED STEEL SHOT TO THE POINT WHERE SAID BEVELED PORTION BEGINS, THEREBY FORMING A SMOOTH SUPPORT SURFACE FOR THE WELD AT THE JUNCTION OF THE VERTICAL PLANAR SURFACES AND THE BEVELED EDGES; FUSION-DEPOSITING WELD METAL IN AND ALONG SAID GAP ON THE TOP LAYER OF SAID SHOT; AND REMOVING SAID ADHESIVE AND SHOT UPON WELD SOLIDIFICATION WHEREBY A SMOOTH CONCAVE WELD SURFACE IS FORMED. 